Abstract

Krüppel-like factor 8 (KLF8) is a transcription factor that we previously identified as a downstream target of FAK in the cell cycle regulation and is up-regulated in human breast and ovarian cancer cells and tumor tissues. We have recently showed that overexpression of KLF8 in human breast epithelial MCF-10A cell promotes the epithelial-mesenchymal transition (EMT) and the acquisition of invasive phenotype. In this study, we report that inducible expression of KLF8 is associated with an increase in the promoter activity and expression of the matrix metalloproteinase 9 (MMP9). We show that inducible expression of KLF8 significantly increased the mRNA expression level of MMP9 as well as the activity of MMP9 in the condition medium. Furthermore, we show that the MMP inhibitor GM6001can decrease the invasive capability of MCF-10A expressing inducible KLF8 using Matrigel invasion assay. Using promoter luciferase reporter assays, we demonstrate that KLF8 strongly promotes the activity of MMP9 promoter in MCF-10A cells. The knockdown of KLF8 by inducible shRNA decreases MMP9 expression and the MMP9 activity in condition medium as well as the cell invasion in metastatic breast cancer cell line MDA-MB-231 cells. In 3D culture, induction of KLF8 expression can disrupt the normal acinus phenotypes of MCF-10A cell, which can be partially rescued by GM6001. Conversely, knockdown of KLF8 or GM6001 treatment can prevent the malignant morphology formation of MDA-MB-321 cells. Taken together, these results highlight a novel role for KLF8 in the activation of MMP9 transcription and breast cancer cell invasion. Experiments are in progress to determine the in vivo role of KLF8 for breast cancer invasion and metastasis using a xenograft mouse model of human breast cancer.